Pepakura Designer is a 3D model viewer that also makes them a printable version. If you are into paper folding, or origami, this program will most probably help you eliminate all that spare time you have.

Pepakura won't allow you to create 3D models, but only view them. If you get creative and want to make your own model, you can use software like Google SketchUp or AutoCAD and open the models created in them. Pepakura supports the following file types: .pdo, .6kt, .6ks, .obj, .dxf, .mqo, .3ds, .lwo, .stl, .kmz and .kml.